Thanks for the replies.
In general, I'd say this much swap is not a good
Even if I do dumb things like this, as well as playing with 20MB+ images
I have 3x HDD - would 3x SWAP partitions of ~350MB spread over each one
be more efficient?
Even 2 GB of
swap will give you problems, realistically. If you ever get to the point
where you are actively using that much ram and are paging out to 2GB or
4 GB of swap, your system will probably be useless anyway, due to heavy
paging to disk.
The system was actually pretty responsive still - as far as being able
to browse the web/check email, etc. goes - eventually when it started to
slow down switching between virtual desktops I tried the
Ctrl-Alt-Backspace sequence, but this appeared to do nothing, so used
(at this point I had a blank screen) the SysReq function.
Far better to let the oom-killer take effect earlier
I'm picking you needed to use this because the system was so
unresponsive... and that was probably because it was spending most of
time pushing things in and out of swap.
However, the oom-killer doesn't kill the system, or the kernel. It'll
kill processes that try to request memory when there is no more left -
which is why it killed the process "passkey-agent" in your pasted log
snippet. As I suspect all of your processes were running under your X
session, you could have killed X instead (via ctrl-alt-backspace, for
example). This may not have left your system in a usable state, due to
other processes having been killed, but it would have been safe to
reboot it normally from here.
As mentioned before, apart from pretty heavy swapping (the SWAP
partition was on a 36GB Raptor HDD, so this may have helped the
performance a bit) the system was pretty useable for an hour or so after
this had started :-)
Thanks for the replies - they have increased my understanding a little more!